1. Field of the Invention
The present invention relates to a sheet stacking apparatus that stacks sheets, a sheet storing apparatus that stores sheets, and an image forming apparatus.
2. Description of the Related Art
Some conventional image forming apparatuses, such as copying machines, are equipped with a post-processing apparatus that temporarily stacks a plurality of sheets on a tray, staples the sheets, and discharges the stapled sheets (refer to FIG. 2 in Japanese Patent Application Laid-Open No. 2008-156089). Also, Japanese Patent Application Laid-Open No. 11-199119 discusses an apparatus that moves up and down a bin on which a plurality of sheets are temporarily stacked, nips the plurality of sheets on the bin, and conveys the nipped sheets.
However, Japanese Patent Application Laid-Open No. 2008-156089 does not discuss an apparatus equipped with a plurality of trays for stacking. Also, even if the post-processing apparatus is equipped with a plurality of configurations discussed in Japanese Patent Application Laid-Open No. 2008-156089, the size of the apparatus may increase.
In the case of the configuration discussed in Japanese Patent Application Laid-Open No. 11-199119, since it is necessary to move up and down the bin, on which a plurality of sheets are stacked, a drive source strong enough to bear a high load is required.